The central goal of this project is to define the mechanism of myocardial bioenergetic failure in heart failure (HF) and design therapeutic strategies targeted to improve mitochondrial energy production. We recently found a dramatic decrease in oxidative phosphorylation (OXPHOS) of heart mitochondria in canine moderate severity micromebolism-induced HF. The mitochondrial defect does not lie in the total amount and activity of individual electron transport chain complexes but in their assembly in supercomplexes (respirasomes). Complex IV not incorporated in respirasomes contains an increased content of serine and threonine phosphorylation in mitochodria isolated from HF compared with the control. We hypothesize that HF-induced adrenergic stimulation increases C3^osolic cAMP which is transported into the mitochondrial intermembrane space through the mitochondrial outer membrane voltage-dependent anion channel (VDAC) and activates the mitochondrial cAMP dependent kinase (mtPKA). mt PKA-induced phosphorylation of matrix-exposed serine and threonine residues of cytochrome c oxidase (COX) subunits impairs the incorporation of COX into supercomplexes, reduces the amount of fijnctional respirasomes, and decreases OXPHOS of heart mitochondria. Complexes I and III not incorporated in respirasomes facilitate electron leakage and produce superoxide, which causes oxidative modifications of both mitochondrial matrix and myofibrillar proteins, with decreased contractile performance. Experiments will be performed in the well established canine coronary microembolization model ofHF, transgenic mice and cultured cells. Specific aim 1 wil investigate mitochondrial respirasome organization, OXPHOS, ATP production, and ROS generation in moderate severity and severe canine HF. Specific aim 2 will identify the role of the adrenergic stimulation in disruption of the assembly of mitochondrial respirasomes in HF. Specific aim 3 will delineate the mechanistic pathway responsible for the translation of the adrenergic signal into mitochondrial alterations. Specific aim 4 will identify the specific mitochondrial targets for the cAMP-induced phosphorylation and their functional consequences. Specific aim 5 proposes a rational approach for therapeutic strategies that targets cAMP/mtPKA signaling with the attempt to prevent mitochondrial ROS generation, RELEVANCE (See instructions):